I decided to take a tour of the Tanagar Canyon, after crunching out my last theory. If you haven't seen it, here is the thread, The story we missed, behind the shrines. Breath of the Wild, look for the section titled, "The Forgotten Temple, and the Eighth Heroine," for more background on how the shrines inspired and brought this idea to light. I'm not going to re-post the whole section, hoping that this theory can stand on it's own. A few things I did mention in the other thread, that I do think is important, though, is that the Eighth Heroine is facing the forgotten temple, though not exactly. The Forgotten Temple also looks to have sunken into the ground, or swallowed. This is most obvious by the broken chunks of land that look to have crumbled and now rest on the top of the structure. It also shows in the pillars just outside of the building, which are sunk to different levels (as apposed to having the tops broken off like many other pillars in the game), and are leaned at different freestanding angles. Even the flooring inside the structure looks to have partly given way to some area below, and may still be crumbling away. There is also no water in the canyon, or even anywhere for that water to drain away to, so it is very unlikely that this canyon could have been formed by water flow; a very common way for canyons to be formed. The canyon does have the cluttered appearance of collapsed land having fallen in. This canyon was formed by a collapse.
The southern half of the canyon is decorated by windmills, and there is a single red flag about a third of the way. The windmills look to be more artistic, than for the power production; no electricity, no milling, no work being done. To my knowledge, these only exist in the canyon. This all suggests that their construction has something to do with the event that created the collapse, such as a memorial. The red (and pole) flag could be part of the same memorial, or a separate memorial, commemorating the same event (meaning it would have been placed by a different group). The singular placement, and circular clearing could be an indication of a grave site.
In the thread I mentioned above, I came to the conclusion that there may have been a blending of religions that angered the gods. While exploring the location again, I have come to the realization that it may have also been a powerful attack, originating from the Eighth Heroine, and my previous observations would still be just as valid. The Eighth Heroine has a striking resemblance to the Desert Colossus, from Ocarina of Time. If they are one in the same, Zelda (disguised as Sheik) describes the location as evil. Only a few things change, from the failed attempt at blending religions, versus the direct attack. There is still a high death toll. It is still related to religion. And, I think a road would have still been likely along the majority of the path. The main difference would be whether Hylians carried some of the blame, and how much of that blame would have likely been held against the Gerudo.
The southern half of the canyon is decorated by windmills, and there is a single red flag about a third of the way. The windmills look to be more artistic, than for the power production; no electricity, no milling, no work being done. To my knowledge, these only exist in the canyon. This all suggests that their construction has something to do with the event that created the collapse, such as a memorial. The red (and pole) flag could be part of the same memorial, or a separate memorial, commemorating the same event (meaning it would have been placed by a different group). The singular placement, and circular clearing could be an indication of a grave site.
In the thread I mentioned above, I came to the conclusion that there may have been a blending of religions that angered the gods. While exploring the location again, I have come to the realization that it may have also been a powerful attack, originating from the Eighth Heroine, and my previous observations would still be just as valid. The Eighth Heroine has a striking resemblance to the Desert Colossus, from Ocarina of Time. If they are one in the same, Zelda (disguised as Sheik) describes the location as evil. Only a few things change, from the failed attempt at blending religions, versus the direct attack. There is still a high death toll. It is still related to religion. And, I think a road would have still been likely along the majority of the path. The main difference would be whether Hylians carried some of the blame, and how much of that blame would have likely been held against the Gerudo.